This invention relates to the field of heat stable phenolic resin molding materials. More particularly, this invention relates to the field of thermosetting phenolic resin molding material having superior retention of useful properties during long term exposure at elevated temperatures.
Phenolic, and in particular phenol-formaldehyde polymers reinforced with glass fibers and mineral fillers are well known to those skilled in the art to have excellent dimensional stability, even under high loads and elevated temperatures. In fact, it is commonly known that phenol-formaldehyde compounds withstand thermal degradation at elevated temperatures better than most other common polymeric materials. Nevertheless, greater application and utility of phenolic compositions could be achieved if they were capable of withstanding degradation without appreciable loss of properties with time of aging at even higher temperatures then observed in conventional prior art phenolic molding compounds.